Recuperator



W. HARTWEG June 5, 1956 RECUPERATOR Filed Dec. 2, 1952 I I'll O 0 D O 00 Q Q 0 fzwenior:

WALTER HARTWIG- United States Patent C RECUPERATOR Walter Hartwig, Okeram Harz, Germany Application December 2, 1952, Serial No. 323,564

7 Claims. (Cl. 26320) The present invention relates to a recuperator forheating air, vapors or other gaseous media. Such recuperators are usedin industry in connection with such apparatus such as smelting furnaces,combustion chambers, and the like, for heating by means of otherwiseuseless, highly heated combustion or waste gases discharged therefromair, vapor, or other gaseous media. Of particular significance is theuse of such recuperators as air heaters.

In particular, the invention concerns a recuperator, consisting of anouter wall and an inner steel tube having ribs for spacing the tube fromthe wall. The heat transmitting medium then passes through the tube andthe heat absorbing medium flows through the annular gap between the tubeand the wall. In the case of these recuperators, the heat radiation ofthe hot flue or fuel gases has an important effect in the heating of themedium flowing between the tube and the wall. Known recuperators of thiskind are only suitable for small outputs and cornparatively low flue gastemperatures with a correspondingly low heat output, since suchrecuperators become distorted and useless in a short time with highertemperatures.

The invention aims at providing a recuperator of the afore-mentionedkind which, with a high output and dimensions of any desired size alsocan operate satisfactory at flue gas temperatures of 1300-1350 C. with apreheating of the medium to 800-900 C.

According to the present invention this is obtained by the fact that theouter wall, which is preferably fitted on the outside with a jacket ofmetal sheet or plate, consists of shaped insulating bricks with recessesfor housing the ribs the depth of the recesses corresponding to thelength of the rib minus the width of the gap. These bricks are so formedthat the gap for the medium to be heated between the tube and the shapedbricks may be maintained at the actual width necessary for a highvelocity of the air to be heated and consequently a good heattransmission. The ribs apart from keeping the shaped bricks at adistance from the internal tube, also serve for heat transmission aswell as for stiffening the tube. The gap provided, even if it is ever soslight, is always guaranteed by the distancing. The shaped bricks arealso comparatively rough, so that a strong whirling action is effectedat the same time, which assists the heat exchange considerably. For thispurpose the ribbed tube may also be provided with irregularities or thelike.

The invention will be described further, by Way of example, withreference to the accompanying drawings, in which:

Fig. l is a longitudinal section; and

Fig. 2 is a cross section on a larger scale.

The recuperator consists of an internal tube 1 of suitable heatresistant material such as steel, on which are mounted ribs 2 forstrengthening and to improve the heat exchange characteristics. Aremovable outer jacket 3 is lined with specially shaped bricks 4. Thesebricks are so formed that a gap 5 of the desired width is createdbetween the tube 1 and the bricks 4. As the bricks 4 abut on the ribs 2,the desired spacing of the bricks from the tube is accuratelymaintained. In the case of larger recuperators the internal tube 1 isreinforced by strengthening bands 6. For the inlet and outlet 9 of air,annular spaces 7 and 8 are provided, through which the medium to beheated is equally distributed over the cross Sectional area of the gap5. The medium enters the annular chamber 7 under pressure, which spaceis at the same time adapted as an expansion member for absorbing thedifference in expansion between the tube 1 and the jacket 3, flowsthrough the gap 5 and leaves the recuperator through the annular space8. The heat absorbing medium in this arrangement flows in countercurrentrelation to the flue gas i. e. in the direction of the arrow 10.

between said inner and outer wall members, the inner sur-- face of saidinsulating lining means being spaced from the outer surface of saidinner wall member by a gap having a radial width amounting to a minorfraction of the distance between said inner and outer wall members, saidinner surface of said insulating lining means being formed with axiallyextending grooves respectively receiving said longitudinal rib portionsof said inner wall member, the depth of each axially extending groovebeing substantially equal to the radial width of the longitudinal ribportion projecting therein minus the radial widthof said gap, whereby afluid medium to be heated is forced to pass at relatively high speedthrough said gap for absorbing heat from a fluid medium passing throughsaid inner wall member.

2. A heat exchange apparatus comprising, in combination, an innertubular wall member having axially extending longtiudinal rib portionscircumferentially spaced on its surface; an outer tubular wall membersurrounding said inner wall member and radially spaced therefrom toprovide an elongated annular space therebetween into which saidlongitudinal rib portions of said inner wall member project; inlet meansat one end of said annular space; outlet means at the other end of saidannular space; and an intermediate tubular insulating liningmeansarranged in said annular space between said inner and outer wallmembers, the inner surface of said in-" sulating lining means beingspaced from the outer surface of said inner wall member by a gap havinga radial width amounting to a minor fraction of the distance betweensaid inner and outer wall members, said inner surface of said insulatinglining means being formed with axially extending grooves respectivelyreceiving said longitudinal rib portions of said inner wall member, thedepth of each axially extending groove being substantially equal to theradial width of the longitudinal rib portion projecting therein minusthe radial width of said gap, said gap communicating at opposite endswith said inlet and outlet means, whereby a fluid medium to be heated isforced to pass at relatively high speed through said gap from said inletto said outlet means for absorbing heat from a fluid medium passingthrough said inner wall member.

3. A heat exchange apparatus comprising, in combination, an innertubular wall member having axially extending longitudinal rib portionscircumferentially spaced on its outer surface; an outer tubular wallmember surrounding said inner wall member and radially spaced therefromto provide an elongated annular space therebetween into which saidlongitudinal rib portions of said inner wall member project; and anintermediate tubular insulating lining means formed of segments.composed of insulation bricks arranged in said annular space betweensaid inner and outer wall members, the inner surface of said insulatinglining means being spaced from, the outer surface of said inner wallmember by a gap having a radial'width amounting to a minor fraction ofthe distance between said inner and outer Wall members, the t centportions of the inner surfaces of adjoining bricks being recessed toform axially extending grooves respectively receiving saidlongitudinalrib portions of said inner wallmember, the depth of eachaxially extending groove being substantially equal to the radial widthof the longitudinal rib portion projecting therein minus the radialwidth of said gap, whereby-a fluid medium to be heated is forced to passat relatively high speed through said gap for absorbing heat from afluid medium passing through said inner wall member.

4. A heat exchange apparatus comprising, in combination, an innermetallic tubular wall member having axially extending longitudinal ribportions circumferentially spaced on its outer surface; an outermetallic tnbular wall-member surrounding said inner wall member andradially spaced therefrom to provide an elongated annular spacetherebetween into which said longitudinal rib portions-of said innerwall member project; and an intermediate tubular heat insulating liningmeans arranged insaidiannular space between said inner and outer'wallmembers, the;inner surface of said insulating'lining means being spacedfrom the outer surface of said innerwall member by. a gap having aradial wi th. amounting to a minor fraction. of the distance betweensaid inner and outer wall members, said inner surface of said.insulating lining means being formed with axially extending grooves. respectively receiving said longitudinal: rib portions of said inner;wall-. member, the depth, of each axially extending groove beingsubstantially equal; to. the radial width of the longitudinal ribportion projecting therein minus the radial width of said gap, whereby afluid medium to be heated is forced to pass at relatively high speedthrough said gap for absorbing heat from a fluid medium passing throughsaid inner wall member;

5. A heat exchange apparatus comprising, incombination, an inner steeltubular wall member having axially extending longitudinal rib portionscircumferentially spaced on its outer surface; an outer tubular wallmember surrounding said inner wall member and radially spaced therefromto provide an elongated annular space therebetwecn into which saidlongitudinal rib portions of said inner wall member project; and anintermediate tubular insulatinglining meansformed of segments composedof insulation bricks having rough surfaces arranged in said annularspace between said inner and outer wall members, the inner surface ofsaid insulating lining means being spaced from the outer surface of saidinner wall member by a gap having a radial width amounting to a minorfraction of the distance between said inner and outer wall members, theadjacent portions of the inner surfaces of adjoining bricks beingrecessed to form axially extending grooves respectively receivingisaidlongitudinal,

rib portions of' said inner wall member, the depth of each axiallyextending groove being substantially equal to the radial width of thelongitudinal rib portion projecting therein minus the radial width ofsaid'gap, whereby a fluid mediumto be heated is forced to pass atrelatively high speed through said gap for absorbing heat from a fluidmedium passing through said inner wall member;

6. A heat exchange apparatus comprising, in combination, an inner steeltubular wall member having axially extending longitudinal rib portionscircumferentially spaced on its outer surface; an outer tubular wallmember surrounding said inner wall member and radially spaced therefromto provide an elongated annular space therebetween into which saidlongitudinal rib portions of said inner wall member project; inlet meansat one end of said annular space; outlet means at the other end of saidannular space, said inlet and outlet means each including an annularconduit extending around said inner wall member at opposite endsthereof; and an intermediate tubular insulating lining means formed ofsegments composed of insulation bricks having rough surfaces arranged insaid annular space between said inner and outer wall members, the innersurface of said insulating lining means being spaced from the outersurface of said inner wall member by a gap having a radial widthamounting to a minor fraction of the distance between said inner andouter wall members, the adjacent portions of the inner surfaces ofadjoining bricks being recessed to form axially extending groovesrespectively receiving said longitudinal rib portions of said inner wallmember, the depth of each axially extending groove being substantiallyequal to the radial width of the longitudinal rib portion projectingtherein minus the radial width of said gap, said gap communicating atopposite ends with said annular conduits of inlet and outlet means,whereby a fluid medium to be heated is forced to pass at relatively highspeed through said gap from said inlet to said outlet means forabsorbing heat from a fluid medium passing through said inner wallmember.

7. A heat exchange apparatus comprising, in combination, an innertubular wall member having axially extending longitudinal rib portionscircumfercntially spaced on its outer surface; annular reinforcing meansextending around said inner wall member; an outer tubular wall membersurrounding said inner wall member andradially spaced therefrom toprovide an elongated annular space therebetwcen into which saidlongitudinal rib portions of said inner wall member project; and anintermediate tubular insulating lining means arranged in said annularspace between said inner and outer wall members, the inner surface ofsaid insulating lining means being spaced from the outer surface of saidinner wall member by a gap having a radial width amounting to a minorfraction of the distance between said inner and outer wallmembers, saidinner surface of said insulating lining means being formed with axiallyextending grooves respectively receiving said longitudinal rib portionsof said inner wall member, the depth of each axially extending groovebeing substantially equal to the radial width of the longitudinalribportion projecting therein minus the radial width of said gap,whereby a fluid medium to be heated is forced to pass at relatively highspeed through said gap for absorbing heat from a fluid medium passingthrough said inner wall member.

References Cited in the file of this patent UNITED STATES PATENTS813,918 Schmitz Feb. 27, 1906 1,690,326 Bolling et a1. Nov. 6, 1928FOREIGN PATENTS 120,938 Australia Feb. 21, 1946

